Materials

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Materials Mechanics Laboratory

• Torsion in Circular Sections

Geoffrey Fisher and Ryan Breighner Texas Tech
University Spring 2007
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Definition

• Torsion Angular deflection of a member as the
  result of being subject to a moment (torque)
  applied about the members axis

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Motivation

• The primary application of circular shafts in
  engineering is to transmit power.
• e.g. drive shafts and axels
• Understanding loading and deflection in circular
  shafts allows us to design systems that perform
  optimally and safely

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Torsion Failure

• Ductile failure
• occurs along planes perpendicular to the axis of
  the shaft
• Brittle Failure
• Occurs along 45 angle to the surface

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Torsion Failure
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The Experiments (3)

• Torsional Deflection of a Solid Rod
• Effect of Rod Length on Torsional Deflection
• Comparison of Solid Rod and Tube

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The Objectives

• Experimentally determine shear moduli for the
  materials tested (Exp. 1)
• Observe the influence of shaft length on
  deflection (Exp. 2)
• Observe the advantages of employing hollow
  sections (Exp. 3)

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Setup
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Setup (cont.)
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Setup (cont.)
Load Cell
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Relevant Equations
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More Equations
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Modulus of Rigidity
G80E9
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Overall Rigidity
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Important Stuff to Remember

• Phi is measured in radians when using the
  equations (you will have to convert from degrees)
• G is in units of pressure (GPa or Msi)
• Radians are essentially unitless
• Force the y-intercept of all graphs for these
  experiments through 0.